Free Process Control and Instrumentation MCQs with Answers

• A. Stress
• B. Contraction/expansion due to changes in temperature
• C. Deflection
• D. Strain

Explanation: A dilatometer measures dimensional change, especially expansion or contraction, as temperature changes.

• A. Seebeck effect
• B. Wien's law
• C. Kirchoff's law
• D. Peltier effect

Explanation: A disappearing-filament optical pyrometer compares the brightness of a heated filament with the radiation from the hot body, using the…

• A. Is a constant
• B. Grows exponentially with time
• C. Grows linearly with time
• D. Decays linearly with time

Explanation: A double pole at the origin gives an inverse-Laplace term proportional to t, since L⁻¹{1/s²} = t.

• A. Temperature
• B. Pressure
• C. Flow rate
• D. Concentration

Explanation: Gas chromatography separates components and measures their detector responses, which are converted into the concentration or composition…

• A. All A , B & C.
• B. Reducing the volume of the capillary to a minimum
• C. Reducing the volume of the receiving element to a minimum
• D. Making the volume of thermometer bulb as large as conveniently possible

Explanation: Ambient-temperature effects are reduced by making the bulb volume large and the capillary and receiving-element volumes small, so most of…

• A. Emission spectroscopy
• B. Flame photometry
• C. Polarimetry
• D. Oscillometry

Explanation: Sugar solutions rotate the plane of polarised light, and the angle of rotation is related to concentration, which is the basis of…

• A. None of these
• B. Hydrogen
• C. Nitrogen
• D. Helium

Explanation: Helium remains suitable for gas-thermometer measurements at temperatures below 0°C and is especially useful at very low temperatures…

• A. Bourdon gauge
• B. U-tube manometer
• C. Inclined tube manometer
• D. Pirani gauge

Explanation: A Bourdon gauge is a robust mechanical instrument for measuring the relatively high pressures encountered in an ammonia reactor.

• A. Chromatograph
• B. Polarograph
• C. Refractometer
• D. None of these

Explanation: A polarograph can determine the concentrations of electroactive metal ions, making it useful for analysing the metallic constituents of…

• A. 1 + et
• B. 1 - et
• C. 1 - e-t
• D. 1 + e-t

Explanation: Interpreting the expression as 1/[s(1+s)], partial fractions give 1/s − 1/(s+1), whose inverse transform is 1 − e⁻ᵗ.

• A. Becomes more oscillatory (frequency increases)
• B. Becomes less oscillatory (frequency decreases)
• C. Gets amplified (magnitude increases)
• D. Gets attenuated (magnitude decreases)

Explanation: A linear first-order system preserves the input frequency but its transfer-function magnitude is less than one in the attenuating…

• A. Absolute
• B. Gauge
• C. Absolute as well as gauge
• D. dynamic

Explanation: A barometer measures atmospheric pressure relative to a perfect vacuum, so its reading is absolute pressure.

• A. Flux density
• B. Current
• C. Light intensity
• D. Voltage

Explanation: Photoelectric transducers detect a change in light intensity and convert it into an electrical signal such as current or voltage.

• A. Ice (F.P) and steam (B.P)
• B. Oxygen and sulphur (B.P)
• C. Antimony and silver (F.P)
• D. Zinc (B.P) and mercury (F.P)

Explanation: The listed international temperature fixed points include mercury's freezing point, along with zinc's boiling point, so the pair in option…

• A. Sinusoidal
• B. Step
• C. Ramp
• D. Impulse

Explanation: Bode plots are obtained from the steady-state response to sinusoidal inputs over a range of frequencies.

• A. Level
• B. Outlet flow rate
• C. Both A. & B.
• D. Neither A. nor B.

Explanation: For a single tank, the outlet-flow response to inlet-flow changes has the first-order form 1/(τs+1).

• A. 1
• B. 1/S
• C. 1/S2
• D. 1/(S2 + 1)

Explanation: The transform 1/s² represents a ramp input, whose magnitude increases indefinitely with time, making it unbounded.

• A. s/(Ts + 1)
• B. 1/Ts
• C. 1/(Ts + 1)
• D. None of these

Explanation: A standard first-order system has a single time constant and transfer function 1/(Ts+1), assuming unit steady-state gain.

• A. Accounting for the tube expansion
• B. Increasing the diameter of the tube
• C. Using steel tube in place of glass tube
• D. Filling nitrogen under pressure in the stem

Explanation: Pressurising the stem with nitrogen raises mercury's boiling point and prevents the column from breaking down at higher temperatures.

• A. 0
• B. ½
• C. 1
• D. 2

Explanation: For a unit step, the output is Y(s)=G(s)/s, so the initial value is lim[sY(s)] as s approaches infinity, which equals lim[(s+1)/(2s+1)] =…